1. Layoffs are usually not "you manager fires you on the spot for whatever reason and with no severance/compensation"

2. Layoffs are usually a less common occurrence than firing people. While the US sucks at labor laws in general, there's at least the WARN act for mass layoffs

3. Layoffs are when multiple people are let go at the same time, which is a distinct category from firing a single person

4. Hence there are often separate negotiations and separate clauses in the union contracts regarding firing a single person (one category) and laying off multiple people (a separate category)

Why the hell you're arguing (in extremely bad faith) against labor protections is beyond anyone's understanding